There currently exists an omnidirectional loudspeaker with a spherical membrane, this loudspeaker possessing a wide pass-band and making use of the phenomenon of magnetostriction. This loudspeaker is described, for example, in the application of the European patent No. 0 177 383 filed on Aug. 22, 1985 in the names of the same applicants.
This patent application describes a wide pass-band elastic wave omnidirectional transducer and more specifically a spherical-shaped loudspeaker making use of the phenomenon of magnetostriction.
In one particular embodiment described in this patent, the spherical-shaped omnidirectional loudspeaker is constituted by a strip made of a magnetostrictive material wound into a spiral with an elastic joint joining the spires of the strip; the two extremities of this strip are connected to means so as to apply to the loudspeaker thus obtained, which forms a spherical pulsating membrane, an electric control signal corresponding to the sound waves to be diffused. The two extremities of the strip are situated in two diametrically opposing zones of the pulsating membrane. This loudspeaker also comprises continuous and permanent magnetic polarization means to polarize the pulsating membrane so that the acoustic wave has an amplitude proportional to the control signal applied to the extremities of the strip.
The loudspeaker described in this patent does, however, has one drawback by only exhibiting low power at low frequencies; this imperfection is mainly due to the difficulty of obtaining a significant amplitude of the pulsations of the spherical membrane at low frequencies.